The present invention relates, in general, to electrical power metering apparatus and, specifically, to electrical watthour meter socket adapters and watthour meter sockets.
In the electric utility industry, plug-in, socket-type watthour meters are commonly employed to measure electric power consumption at a residential or commercial building establishment. A socket is mounted on a wall of the residence or building and contains terminals which are connected to electric line and electric load conductors. The terminals are also connected to internal conductors within the socket which extend to jaw contacts positioned to receive the blade terminals of a plug-on watthour meter to complete an electric circuit through the watthour meter between the line and load terminals and the conductors.
One type of meter socket has a ring-type cover which includes an outwardly projecting, annular mounting flange surrounding an opening in the cover through which the blade terminals of a watthour meter extend. The mounting flange is sized to mate with a complementary formed mounting flange on the bottom of the watthour meter.
In high power applications, current levels exceed the ratings of commonly available watthour meters. In these applications, current transformers are placed around the incoming line conductors and connected to watthour meter receiving jaw contacts to enable watthour meters to measure load current and provide a scaled power measurement.
A special socket, referred to as a K-series socket, shown in FIGS. 1–5 has been developed. The socket is designed for single or three-phase power and is designed to carry current up to 400 amps or more. Rigid bus bar terminals are provided in the upper portion of the socket for receiving the line conductors. Similar plate-like bus bar terminals are mounted at the bottom of the socket for receiving the load conductors. A single mounting fastener, such as a threaded stud, is provided on each load bus bar for receiving a rigid load bus bar extending from a watthour meter which is mountable in the socket. Similar mounting fasteners or threaded studs are mounted in a first row on the upper line power bus bars for receiving a separate line bus bar extending from a watthour meter.
As also shown in FIGS. 1–5, shorting bus bars extend between each line bus bar and the corresponding load bus bar provide a power connection from the power distribution line network to the individual load distribution network in a building.
A cover is mountable over the socket and has an aperture formed in a slidable cover portion for allowing an end portion of the watthour meter to extend therethrough for easy viewing of power measurements. The aperture is mounted in a plate slidably captured on the back of the socket cover. The aperture is offset from the center of the plate such that flipping the plate 180° enables the watthour meter when moved from a lowered operative position to a separate upper inoperative position, to extend through the aperture.
In the inoperative position, the line bus bars on the watthour meter are disengaged from the line bus bar fasteners and moved to a separate spaced row of fasteners, also extending from the line bus bars. However, separate electrically insulting posts are provided in a spaced manner from the load bus bar studs for receiving the load bus bars on the watthour meter in the disconnected position. This disconnects the watthour meter from measurement or service and places it in an out-of-service position.
Attempts to use a watthour meter socket adapter for a plug-in watthour meter in a K-series socket have met with limited success. The size and location of the line conductor insulator blocks, the ground terminal connector and the ground terminal insulator block necessitated socket adapter bus bars having a smaller cross-section than required for current applications up to 400 amps. In addition, additional features and refinements added over time such as cutouts in the sidewall of the socket adapter to accommodate the insulator blocks and ground terminal, make use of the socket adapter difficult without first removing the additional features and refinements.
As is evident from FIGS. 1–5, a specially designed watthour meter with rigid bus bars is necessary for mounting in the K-series socket in both the power measurement and non-power measurement positions. The shape, thickness and spacing of the meter bus bars must also take into account a ground terminal and associated insulator block and insulator blocks between the line bus bars. As a result, prior K-series sockets have not been able to successfully receive watthour meter socket adapters designed for receiving standard, plug-in watthour meters.
In electrical power service sites, it frequently becomes necessary to up grade the electrical power service to supply higher current to the customer site. At high current levels, current transformers are employed to provide lower current levels which can be metered by watthour meters. However, such current transformers require special mounting in a socket which increases installation time and results in a higher installation cost.
It is believed that there still is a need for a watthour meter socket adapter which can be successfully employed in a K-series watthour meter socket. It is also desirable to provide a watthour meter socket adapter for mounting a plug-in watthour meter in a K-series meter socket which can be economically constructed with minimal modification to existing watthour meter socket adapter designs. It would also be desirable to provide a current transformer mounting apparatus which fits within an existing K-series meter socket footprint for reduced installation time and costs when it becomes necessary to increase power to a customer site.